JPH0634437A - Integrated nonlinear waveguide type spectrometer - Google Patents

Abstract

PURPOSE: To realize the integration of a spectrometer by providing a non-linear waveguide where a raised guide shape having a multi cycle structure comprising a plurality of composite semiconductor layers forms a circular arch having a specific radius of curvature, and an organic body-dielectric body waveguide refracting from the focus plane of a reflection mirror of an organic material plate on a dielectric layer. CONSTITUTION: Light radiation of a various wavelengths is reverse-propagated in the direction, mutually reversal, supplied at both ends of a raises guides. With no change in reference radiation w0, the radiation in the opposite direction is injected at various wavelengths in the entire range. Owing to non-linearity of the raised guide 12, synthesized frequency signal is introduced in upward direction of a reflection mirror 16, and then bounced into an organic layer 15 of an organic body-dielectric body waveguide 18, and propagated, in parallel to surfaces 20 and 21, to the reflection light 17, and then re-refracted at the opposite end part of a waveguide 14. A signal 22 from the guide 12 is combined to the waveguide 18 through reflection to light with the mirror 16. Another reflection mirror 17 is used to combine the light from the surface of a detection waveguide. With this, the signal from an integration structure becomes visible, so the integration of a detector with a circuit becomes possible.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to integrated nonlinear waveguide spectrometers.

[0002]

BACKGROUND OF THE INVENTION Optical spectrometers are waveguide devices that use back-propagating χ ² nonlinear waveguide interactions to produce the required chromatic dispersion. In these devices, the reference guide mode interacts with the back-propagating input infrared signal to produce a surface emitting composite frequency signal. The angle at which the upconverted visible signal is emitted is a function of the difference between the reference guiding mode and the wavelength of the input signal. By fixing the reference wavelength, the frequency spectrum of the input signal is mapped to the angular spectrum of the upconverted signal in the far field. The physical principle of a non-linear parametric waveguide spectrometer is shown in FIGS. The non-linear waveguide acts as a diffraction grating in a conventional spectrometer. Two counter-propagating waves, one of which is the reference mode and the other of which is the input signal, interact to generate a surface-radiation-synthesized frequency signal that radiates from the upper surface of the waveguide at an angle limited by the law of conservation of momentum. To do. If one of the counter-propagating beams (reference beam) has a fixed wavelength, the frequency spectrum of the other counter-propagating beam (input signal) is mapped in the far field to the angular spectrum of the composite frequency signal. For example, Earl Normandin
(R. Normandin) et al. “Monolithic, Surface-Emittin
g Semiconductor Visible Lasers and Spectrometers f
or WDM Fiber Communication System ”, IEEE Journal
of Quantum Electronics, Vol.27, No.6, June 1991, pag
es 1520-1530 and D. Vakhshoori
And “Integrable S” by W. Wang
emiconductor Optical Correlator Parametric Spectro
meter for Communication Systems ”, Journal of Lig
htwave Technology, Vol.9, No.7, July 1991, pages 906-9
See page 17.

A non-linear waveguide structure that would be effective in generating green or blue light from radiation injected into the non-linear waveguide is D. Vakhshoor.
Conference on Lasers and Electro-Optics by i) etc.
Technical Digest, Series 1991, (Optical Society of A
(merica, WAshington, DC) Vol.10, page 134 and Conference on Lasers by R. Normandin and RL Williams.
and Electro-Optics Technical Digest, Series 1991,
(Optical Society of America, WAshington, DC) Vol.1
0, page 136 and D.Vakhshoori
“Blue-Green Surface-EmittingSecond Harmon by
ic Generation of (111) B GaAs ”, Applied Physics Let
ters, Vol.59, No.8,19 August 1991, pages 896-898,
“Analysis” by D. Vakhshoori
of Visible Surface-Emitting Second-Harmonic Gener
ations ”, Journal of Applied Physics, Vol.70, No.10,
15 November 1991, pages 5205-5210 Suggested by. Such a structure would include a multi-layer structure composed of alternating composite semiconductor layers in pairs, with each layer in the pair having a different configuration than the other layers in the pair. However, it would be more desirable to provide a non-linear parametric spectrometer with an imaging device that can map near-field to far-field on a composite semiconductor substrate.

[0004]

The present invention embodies the integration of a nonlinear waveguide spectrometer with a polyimide waveguide focus reflector. Waveguide spectrometers use nonlinear backpropagating χ ² interactions to simulate the behavior of a diffraction grating to produce the required chromatic dispersion. Organic-dielectric (eg polyimide / SiO ₂ ) waveguides and 45 ° RIE-etched mirrors for mapping near-field to far-field to separate various wavelength components are used for concave focus integrated reflection. Assembled to simulate a mirror. The spot size measured in the focal plane of the reflector was about 0.7 μm, corresponding to a spectral resolution of about 1.6 Å according to theoretical predictions. The device has good spectral resolution, but the actual conversion efficiency is less than the theoretical prediction. When a 100 mW reference and input signal is used, the converted signal is theoretically 0.
It will be on the order of 1 mW. Even for low signal output levels, the present integrated device can detect applications where the visible output is available and high output conversion efficiency is not required (ie, 1.5 μm and 1.3 μm infrared signals can be detected. Integrated with a silicon PIN detector and circuitry that cannot.

[0005]

DETAILED DESCRIPTION OF THE INVENTION The present invention is an integrated optical device in which a nonlinear parametric waveguide spectrometer is integrated with an organic-dielectric waveguide. A 45 degree angle reflector mirror etched by reactive ion etching (RIE) reflects the surface light generated by the non-linear ridge guide parallel to the surface and couples into the organic-dielectric waveguide. Made on both ends of the waveguide. In a preferred embodiment, an integrated non-linear waveguide spectrometer with a resolution of 1.6 uses a non-linear periodic GaAs / AlGaAs raised guide structure with a circular area of 2 mm in length and a polyimide / SiO _{2 of} 4 mm in length. It was formed on a GaAs substrate with a width of 4 mm and a length of 7 mm by integrating it with a waveguide.

An integrated optical device is shown schematically in FIGS. 1 and 2 of the drawings. 1 is a plan view of the integrated optical device, and FIG. 2 is a side sectional view of the integrated optical device. For illustration purposes, the dimensions of the integrated device are not scaled.

An integrated optical device, generally designated by the numeral 10, is a crystalline composite semiconductor substrate 11, a multi-quantum well region 12 including raised guides 13, a dielectric layer 14, and 45 on both ends.
° Organic polymer material layer 15 with reflectors 16 and 17
Including and Dielectric layer 14 and organic layer 15 form an organic-dielectric waveguide, generally designated as 18. Dielectric materials have a lower index of refraction than organic materials,
Form a cladding layer for the organic-dielectric waveguide.

The integrated optical device is fabricated on a substrate 11 having a region 12 formed of alternating thin film layers. Fabrication comprises etching a set of grooves 19 in the region 12 to define the insulated raised guides 13,
The method includes depositing the dielectric layer 14 on the entire upper surface 20 of the region 12 and the groove 19, and depositing a light-permeable organic polymer material layer 15 on the entire surface 21 of the dielectric layer 14. The planar organic-dielectric waveguide 18 is formed by limiting the waveguide contour to the organic layer and etching the organic layer to the desired shape. The raised guide 13 has a groove 19 that is dry-etched to maintain the flatness of the wafer.
Limited by Except for the grooves, the wafer is kept flat to facilitate the subsequent fabrication of the organic-dielectric waveguide 18 and 45 ° mirrors 16 and 17. The raised guide 13 shown by a dotted line in FIG. 1 is composed of a circular arcuate shape 23 at an intermediate portion and straight line portions 24 at both ends. The small circular arch can smoothly interconnect the circular arch 23 with the straight portion 24. In an exemplary embodiment,
The substrate 11 is made of GaAs and has a region 12 and a raised guide 13.
Consists of GaAs / AlGaAs multi-layer, multi-period structure. Each cycle is
It is formed by a thin film layer of GaAs and a thin film layer of Al _x Ga _1-x As when _x is in the range of 0.7 to 1. The thickness of each layer is 1/2 wavelength (λ
Equal to / 2). In the preferred embodiment, the dielectric material is SiO ₂ (n = 1.47) and the organic material is polyimide / n = 1.6 forming a polyimide / SiO ₂ waveguide. The substrate 11 has a thickness of about 150 μm, the region 12 has a thickness of about 1.5 μm, the groove 19 has a width of 1 to 2 μm and a depth of about 2 μm, and the raised guide has a width of 2 to 3 μm and a height of about 2 μm.
The dielectric layer has a thickness of about 0.5 μm, and the organic layer 15 has a thickness of 2 to 3 μm. The entire device is 4 mm long
The waveguide 18 having a width of about 2 mm is provided, and the size is about 4 × 7 mm. The reflectors 16 and 17 are limited to a circular arc similar to the circular arc of the raised guide. The circular bow has a radius of curvature of 4 mm. The 45 ° mirror is incorporated by reference herein, L. A. Cordulin (L.
A. Coldrean) and Jay A. Lenzler (JARentsc
hler) by "Directional Reactive-Ion-Etching of In
P with CL ₂ Containing Gases ", Journal of Vacuum Sci
ence Technology, Vol.19, No.2, July / August 1981, pages
It is etched by reactive ion etching (RIE) in a manner similar to the technique disclosed in 225-230.

In operation, light radiation of various wavelengths
It is supplied to both ends of the raised guide 12 and as a result back-propagates in opposite directions. The radiation entering one direction of the ridge, which represents the reference radiation ω ₀ , remains unchanged, but the radiation supplied from the opposite direction can be injected at various wavelengths in the entire range. Due to the non-linearity of the ridge guides, the composite frequency signal is directed in the upward direction towards the 45 ° mirror 16 where it is 90 ° to the right towards the organic layer 15 of the organic-dielectric waveguide 18. It is bounced back and propagates parallel to the surface 20 or 21 in the direction of the reflector 17, where the radiation is refracted again at the opposite end of the waveguide 14. The upconverted signal 22 from the raised guide is coupled into the organic-dielectric waveguide by reflection to the right of the 45 ° mirror 16 so that it forms a circular phase front and is 4 mm away from the waveguide. It will focus on the focal plane point. In that focal plane, another 45 ° mirror is used to couple the light exiting the surface of the detection waveguide. The propagation direction of the radiation emitted from the optical waveguide is determined by the tilt direction and angle of the reflecting mirror 17. In this case, the reflector is at 45 ° to the flat surface of the waveguide, so that the radiation is refracted in the upward direction and can be detected there. The opposite 45 ° reflector can be used to couple the signal back to the surface 19 at or on the substrate for detection with the integrated detector array in the focal plane.

The resolution of a conventional spectrometer is limited as the change in input wavelength that moves the spatial position of the signal from its peak point to its first local minimum. In this case, for a focus reflector eg 16 which is calibrated by a 2 mm long non-linear ridge guide eg 13 at the center of the reflector due to the spatial position of the signal peak and the first local minimum in the focal plane. The angles that can be defined are as follows.

[0011]

[Equation 1] Where λ _s , n and d are the composite frequency wavelength,
Effectiveness index of polyimide / SiO ₂ waveguide, aperture of curved mirror. On the contrary, the change of the radiation angle due to the change of the input wavelength (FIG. 3) is as follows.

[0012]

[Equation 2] Here, λ, λ ₀ , n, n ₀ , and n _s are the GaAs / AlG for the input fundamental and reference wavelengths and the input and reference beams, respectively.
aAs Elevation guide effective index, polyimide / SiO ₂ waveguide effective index for composite frequency signals.

In the third line of equation 2, λ is approximately λ ₀ and λ ₀
Is about 1.0 μm and is obtained by approximating the values of the above parameters. The resolution of the spectrometer is then estimated as:

[0014]

[Equation 3]

The output measured from the reflector 17 is recorded in black and white opposite. FIG. 6 shows the two dots that represent the visible blue signal emanating from the 45 ° reflector 17 and lie in the focal plane of the circular reflector. The laser light from Nd: YAG is
It was used as a reference beam ω ₀ having a wavelength λ ₀ = 1.064 μm. The tunable Ti-sapphire laser light has wavelengths λ ₁ = 0.9734 μm and λ ₂ =, respectively.
Used as input signals ω ₁ and ω ₂ with 0.9724 μm. For recording, first adjust the adjustable laser with λ ₁ =
Adjusted to 0.9734 μm, sending the reference beam and the first input signal beam across the ridge guide, exposing the thin film to the upconverted signal, and then moving the tunable laser to λ without moving the thin film. ₂ = 0.9724 μm, and re-exposing the same film at the next location to the next upconverted signal. The signals upconverted from λ ₁ and λ ₂ are spectrally 1 nm apart and the spots are spatially separated by 4 μm in the focal plane. The signal spot size (FWHM) was measured to be about 0.7 μm for each of the two wavelengths, which theoretically corresponds to a spectral resolution of 1.6. Several small radius spots (not shown) appeared around the two major peaks. These are probably the result of the large number of reflections and possible deviations of the bent GaAs / AlGaAs nonlinear waveguide from its ideal circular arch. The coupling loss from the non-linear raised guide to the organic-dielectric waveguide and the propagation loss of this waveguide at the wavelength of the blue upconverted signal appear to be large. Therefore, the signal output was much less than the value predicted by theory. This signal, when 100mW reference and input signal is used,
Theoretically, it should be on the order of 0.1 mW. Nevertheless, since the signal from the integrated structure is visible to the naked eye, the device is integrated with the silicon detector and the circuit, ie the silicon PIN detector, which cannot detect 1.5 μm and 1.3 um infrared signals. And for applications requiring integration with circuits.

An integrated spectrometer with a non-linear GaAs / AlGaAs raised guide was grown on 100 GaAs substrates. This means that both TE and TM modes must be present due to the generation of synthetic frequencies that are repulsive in terms. This is practically for a non-linear parametric waveguide spectrometer, since by combining the reference beam as the TM mode and the input signal as the TE mode, which is retroreflected, no second harmonic is generated in the first approximation. It will be an advantage.

Additional advantages and variations will readily suggest themselves to those skilled in the art. Accordingly, the invention in its broader aspects is not limited to the specific details, devices shown, and the exemplary embodiments shown and described. Thus, various modifications may be made without departing from the spirit or scope of the general inventive concept as limited by the appended claims and their equivalents.

[Brief description of drawings]

FIG. 1 shows an integrated spectrometer with a curved GaAs / AlGaAs raised guide and a polyimide / SiO ₂ plate waveguide with bent reflectors at both ends positioned at 45 ° to the plane of the raised guide. It is a figure which shows the top view of a schematic diagram.

[Fig. 2] A 45 ° angle reflector reflects surface light on polyimide / SiO ₂
FIG. 6 shows a side cross-sectional view of a schematic diagram of an integrated spectrometer coupled into and out of a plate waveguide.

FIG. 3 shows how the frequency spectrum of the input signal maps to the angular spectrum of the upconverted signal in the far field.

FIG. 4 shows how the frequency spectrum of the input signal maps to the angular spectrum of the upconverted signal in the far field.

FIG. 5 shows a schematic diagram of a backpropagating raised guide with a fixed wavelength reference mode and input signals of various wavelengths.

FIG. 6 shows a schematic diagram of two spots corresponding to a blue signal in the focal plane resulting from the interaction of a reference wavelength and two types of Ti-sapphi laser wavelengths.

[Explanation of symbols]

 10 Integrated Optical Device 13 Raised Guide 16, 17 Reflector 18 Organic-Dielectric Waveguide 19 Groove

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Darijos Vaksholi United States 07076 New Jersey, Scotch Plains, Apartment Men, Park Avenue 519 (72) Inventor Joe John Zickzick United States 07832 New Jersey, Colombia, Root 1

Claims (8)

[Claims] 1. An integrated optical device comprising a non-linear parametric waveguide spectrometer on a substrate, and an elongated organic-dielectric waveguide transversely positioned on the non-linear waveguide. In the non-linear waveguide, the shape of the central portion of the raised guide forms a circular arc shape having a preselected radius of curvature, and the raised guide has a structure in which one layer in each set is different from that of the other set. A multi-periodic structure composed of a plurality of sets of composite semiconductor layers, wherein the organic-dielectric waveguide is placed on a thin dielectric layer.
The dielectric layer, which has a shape of an elongated flat plate made of an organic material and has a lower refractive index than the organic material, acts as a bottom clad layer for the organic material, and the flat plate of the organic material has both end portions. 45 degree reflectors, each reflector being defined by a circular arc having the same radius of curvature as the raised guide, one reflector being mounted on the circular arch and emitting visible radiation from the raised guide. That the radiation is deflected into a flat plate of organic material, hits a mirror at the opposite end of the flat plate, and then refracts from the focal plane of that mirror. Characterized integrated optical device. 2. The apparatus of claim 1, wherein the raised guide is defined by a set of grooves formed in the surface of the multi-periodic structure on a GaAs substrate, the multi-periodic structure being GaAs / AlGaAs.
A device composed of a plurality of cycles of alternating layers of. 3. The device of claim 2, wherein each of said sets comprises a GaAs layer and Al _x Ga when _x ranges from 0.7 to 1.
_A device consisting of _1-x As layers. 4. The device of claim 2, wherein the thickness of each layer is equal to one-half the wavelength of visible radiation generated by the raised guide. 5. The device according to claim 1, wherein the flat plate made of an organic material is made of polyimide. 6. The device of claim 1, wherein the dielectric material comprises SiO ₂ . 7. The apparatus of claim 1, wherein the reflector is tilted 45 ° in the same direction with respect to the plane of the raised guide,
As a result, the radiation arriving at the other reflector is directed away from the substrate in an upward direction. 8. The apparatus of claim 1, wherein the reflector at the opposite end of the plate is mounted on a raised guide at 45 °.
A device that is tilted at 45 ° in the direction opposite to the direction of the reflector so that the radiation reaching the other reflector is directed towards the substrate.